Urinary tract infection (cystitis)
Burning, frequency and cloudy urine in a young woman: treat without a dip. Send a culture in men, pregnancy and anyone over 65.
A 28-year-old woman has had burning on passing urine and frequency for 2 days. No fever, no loin pain, no vaginal discharge. She is not pregnant. Dipstick: nitrites positive, leucocytes positive.
A 34-year-old man has the same symptoms. A 24-year-old pregnant woman has nitrites on a routine dipstick but no symptoms.
Who gets 3 days of antibiotics, who needs a culture and longer treatment, and who needs treatment without symptoms?
- Confirm it is a lower UTIDysuria, frequency, urgency, suprapubic pain. No fever, rigors or loin pain.
- Ask aboutPregnancy, vaginal discharge (STI or thrush), diabetes, catheter, recent antibiotics.
- Women under 65, typical symptomsTreat without culture: nitrofurantoin for 3–5 days or fosfomycin single dose.
- Men, pregnancy, recurrent, failed treatmentSend urine culture before antibiotics.
- PregnancyTreat even without symptoms (asymptomatic bacteriuria), with a culture.
- Fever, loin pain, vomitingPyelonephritis: different treatment.
- AdviceFluids, paracetamol, return if fever or loin pain.
- Fever, rigors, loin pain
- Vomiting and unable to take tablets
- Pregnancy with symptoms of pyelonephritis
- Sepsis
- Visible haematuria persisting after treatment
- Recurrent UTI in men
- Pyelonephritis
- STI (chlamydia, gonorrhoea)
- Vaginal candida
- Pregnancy
- Kidney stone
- Bladder cancer (haematuria in older smokers)
- Prostatitis in men
| Nitrofurantoin | 100 mg modified-release twice daily for 3–5 days (women), 7 days (men) |
| Fosfomycin | 3 g single dose (women) |
| Avoid nitrofurantoin | eGFR below 45 (or below 30 for short courses), near term in pregnancy |
| Men | 7 days of treatment and a culture |
| Pregnancy | 7 days, culture before and after |
| Over 65 | Don't use dipstick alone, treat on symptoms and culture |
Check every dose against a current drug reference and your hospital protocol.
On this page
Diagnosis
UTI likely: treat
- Culture
- consider other causes
Think STI or thrush first
Over 65 or with a catheter: don't use a dipstick to diagnose, because many have bacteria without infection. Treat new symptoms with a culture.
Who needs a urine culture?
- Men.
- Pregnancy.
- Over 65 with symptoms.
- Recurrent UTIs or failed treatment.
- Catheter.
- Visible haematuria.
- Atypical symptoms or suspected pyelonephritis.
Differential diagnosis
| Condition | Clues |
|---|---|
| Pyelonephritis | Fever, loin pain, vomiting |
| Chlamydia or gonorrhoea | New partner, discharge, intermenstrual bleeding |
| Vaginal candida | Itch, thick white discharge |
| Kidney stone | Colicky loin to groin pain, blood |
| Urethritis in men | Discharge, STI risk |
| Prostatitis | Perineal pain, fever, tender prostate |
| Bladder cancer | Painless haematuria, older smoker |
| Interstitial cystitis | Chronic pain, negative cultures |
Treatment
Pakistan: resistance to ciprofloxacin and co-trimoxazole in E. coli is very high. Avoid them as first choice for simple cystitis. Follow your hospital's antibiogram.
Special situations
- Pregnancy: treat all bacteriuria. Nitrofurantoin (avoid at term) or cefalexin, 7 days. Culture after treatment to confirm clearance.
- Men: 7 days, culture. Think prostatitis if feverish with perineal pain.
- Recurrent (2 or more in 6 months, or 3 in a year): culture each episode, check glucose, consider imaging, advice on fluids, post-coital voiding; prophylaxis after specialist advice.
- Catheter: only treat if symptomatic. Change the catheter and take the sample from the new one.
- Diabetes: higher risk of complications; lower threshold for culture.
Common mistakes
- Treating a positive dipstick in an elderly patient without symptoms.
- Using ciprofloxacin first line for simple cystitis.
- Giving nitrofurantoin with poor kidney function.
- Missing an STI.
- 3 days for a man.
- Not treating asymptomatic bacteriuria in pregnancy.
Frequently asked questions
What is the first-line treatment for an uncomplicated UTI in women?
Nitrofurantoin modified-release 100 mg twice daily for 3–5 days, or fosfomycin 3 g as a single dose.
Who needs a urine culture?
Men, pregnant women, people over 65, recurrent or failed treatment, catheterised patients and suspected pyelonephritis.
Should asymptomatic bacteriuria be treated?
Only in pregnancy and before some urological procedures.
How long should a man's UTI be treated?
7 days, with a urine culture.
Test yourself
Exam-style questions on this guide, from our two question banks. Choose an answer to see why each option is right or wrong.
1. A 26-year-old non-pregnant woman has dysuria, frequency and cloudy urine. No fever or loin pain. What is the best first-line treatment?
Answer: Nitrofurantoin for 3 days. Uncomplicated cystitis in women: nitrofurantoin 100 mg MR twice daily for 3 days, or fosfomycin 3 g single dose.
- Ciprofloxacin for 7 days: High resistance; not first-line.
- Co-trimoxazole for 3 days: High resistance in Pakistan.
- IV ceftriaxone: Not needed for cystitis.
- No antibiotic until culture: Typical symptoms can be treated empirically.
2. In which patient should asymptomatic bacteriuria be treated?
Answer: A pregnant woman. Asymptomatic bacteriuria is treated in pregnancy because it raises the risk of pyelonephritis and preterm birth.
- A diabetic man: Not indicated.
- An 80-year-old in a care home: Treatment causes harm without benefit.
- A young non-pregnant woman: Not indicated.
- A patient with a long-term catheter: Don't treat without symptoms.
3. Why is a urine dipstick not used to diagnose UTI in patients over 65?
Answer: Bacteria in the urine without infection are common at this age. Asymptomatic bacteriuria is common in older people, so positive dipsticks lead to overtreatment. Diagnose on symptoms and culture.
- Dipsticks don't detect nitrites in older adults: Not the reason.
- Dipsticks are too expensive: Not the reason.
- Older patients can't give samples: Not the reason.
- Leucocytes are always negative: Not true.
4. A 40-year-old man has a first episode of uncomplicated-looking cystitis confirmed on culture. What is appropriate after treatment?
Answer: Investigate the urinary tract. UTIs in men are considered complicated; consider prostatitis, outflow obstruction, stones or structural abnormalities. Treat for 7 days (14 days if prostatitis suspected), and arrange ultrasound of the urinary tract and post-void residual (± PSA after infection settles). Women with uncomplicated cystitis need 3–5 days of nitrofurantoin or fosfomycin without imaging.
- No further action: UTI in men is uncommon and needs investigation.
- Long-term prophylaxis immediately: Investigation should come before prophylaxis.
- Cranberry juice only: Cranberry juice has no evidence in men.
5. A 6-month-old has a first febrile UTI (E. coli) that responds quickly to antibiotics. What imaging is recommended?
Answer: Renal and bladder ultrasound. Febrile UTI in infants: urine sample by clean catch/catheter, treat promptly (oral antibiotics if well; IV if < 3 months or unwell). Renal/bladder ultrasound after first febrile UTI in infants to detect hydronephrosis/obstruction. MCUG for abnormal ultrasound, recurrent or atypical UTI (to detect vesicoureteric reflux, posterior urethral valves). DMSA scan for renal scarring in recurrent/atypical cases.
- No imaging in any infant: Infants need an ultrasound.
- Immediate MCUG for all: MCUG is not routine after a first simple UTI.
- CT abdomen: CT exposes to radiation and is not indicated.
6. The transitional epithelium lining the urinary bladder is derived from which germ layer?
Answer: Urogenital sinus endoderm. The bladder develops from the upper part of the urogenital sinus, which comes from the cloaca (endoderm). The trigone is first formed from the mesonephric ducts (mesoderm) but its lining is later replaced by endoderm. The muscle wall comes from splanchnic mesoderm.
- Surface ectoderm: Forms the epidermis and the distal anal canal lining.
- Intermediate mesoderm: Forms the kidneys and gonads.
- Neural crest cells: Forms melanocytes, adrenal medulla and ganglia.
- Splanchnic mesoderm: Forms the bladder muscle, not its lining.
7. What is the most common cause of traveller's diarrhoea?
Answer: Enterotoxigenic E. coli. ETEC produces heat-labile toxin (raises cAMP) and heat-stable toxin (raises cGMP), causing watery diarrhoea without blood. It is usually self-limiting; treat with fluids, and in severe cases azithromycin or a fluoroquinolone.
- Shigella dysenteriae: Causes bloody dysentery.
- Vibrio cholerae: Causes rice-water stools in outbreaks; less common in travellers.
- Entamoeba histolytica: Causes bloody diarrhoea and liver abscess.
- Clostridioides difficile: Follows antibiotic use.
References and dose sources
- NICE NG109: Urinary tract infection (lower), antimicrobial prescribing
- UKHSA: Diagnosis of urinary tract infections
- Nitrofurantoin dosing: Drugs.com: Nitrofurantoin dosage (see also our nitrofurantoin dose page)
- Fosfomycin dosing: Drugs.com: Fosfomycin dosage (see also our fosfomycin dose page)
- Cefalexin (cephalexin) dosing: Drugs.com: Cephalexin dosage (see also our cefalexin (cephalexin) dose page)
- Paracetamol dosing: Drugs.com: Acetaminophen (paracetamol) dosage (see also our paracetamol dose page)
International guidance is linked where it reflects good practice. Where your hospital’s protocol differs, follow your hospital.